A structural and functional relationship in the mechanism by which glycoprotein hormones (thyrotropin (TSH), luteinizing hormone (LH), human chorionic gonadotropin (hCG), and follicle-stimulating hormone (FSH), certain bacterial toxins (cholera and tetanus, for example), and the antiviral protective agent, interferon, transmit their message through the cell membrane has been further defined. Studies have been initiated to explore the importance of these relationships to the expression of thyroid hyperfunction in Graves' disease, to the autoimmunity of Graves' disease, to the sympathetic overactivity syndrome of tetanus, to the ability of hormones to modulate the oncogenic state, and to the mechanism by which toxins impose their pathological effects. Studies have also been initiated to evaluate the role of membranes in thyroglobulin biosynthesis and thyroglobulin biodegradation to T3 and T4.